Method of heat transfer



May 7, 19 35.

H. H. DOW 2,000,886

METHOD OF HEAT TRANSFER Filed Nov. 2, 1931 3 Sheets-Sheet 1 ATTORNEY May 7, 1935.

Pounds Pressure Absolute in o.

H. H. DOW 2,000,886

METHOD OF HEAT TRANSFER Filed Nov. 2, 1931 5 sheets-sheet 2 parpressure of D/phenyl 0x162 and n al zr O Poinfs determined cxpzrimantall x 1 Point; data-mined by calculation.

Atmos.

Vacuum in inc/m5 0f Marcury 450 500 550 6,00 Dg.Cnt 842 332 I022 I112 Da .F a/1r,

BY Jamal ATTORNEY Fig; Z.

meme May 7, 1935 UNITED STATES 2,000,886 METHOD or HEAT TRANSFER,

Herbert 11. Dow, deceased, late of Midland, Mich.,

by Willard H. Dow and Clara Turner, administrators, Midland, Mich., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Michigan Application November 2, 1931, Serial No. 572,741 x 2 Claims. (Cl. 122-33) The present invention relates to transferring heat by means of a high boiling point compound, specifically diphenyloxide, and more particularly to a method of and apparatus for generating power wherein two fluids, one of relatively high boiling point and the other of relatively low boiling point are employed, instead of just a single fluid as in the case of the ordinary steam boiler. It has longbeen known that the temperature range of the thermodynamic cycle may be increased and the advantages of generating vapor at the higher temperature ranges realized by utilizing a fluid,'such as mercury, evaporating it in a boiler, converting a. portion of the heat energy of the resulting vapor into mechanical work, condensing the vapor and transferring its remaining available heat to water and utilizing the heat energy in the steam thus generated to produce mechanical work. The present application is a continuation in part of copending application,

Serial No. 91,088, filed February 27, 1926, which application has now been abandoned in favor of the present! application.

An object of the present invention is to provide a new and highly advantageous heat transfer agent consisting essentially of diphenyloxide.

To the. accomplishment of the foregoing and relatedends, the invention, then, consists of the steps and means hereinafter fully described and particularly pointed out in the claims, the annexed drawings and the following description setting forth in detail certain mechanism embodying the invention, such disclosed means constituting, however, but one of several mechanical forms in which the principle of the invention may be used.

In said annexed drawingsz- Fig. 1 is a diagrammatic view of the bifluid power generating system illustrating one mode of using the aforesaid novel heat transfer agent;

Fig. 2 is a chart showing the vapor pressures of diphenyloxide and water, respectively; and Fig, 3 is a temperature-entropy diagram of diphenyloxide and of water.

The bifluid system, illustrated in Fig. 1 com prices a primary vapor generator A and a secondary generator or condenser boiler B. Generator A includes connected combustion chambers I and 2, wherein pulverized fuel is to be burned, such fuel being introduced through nozzles 3 and. 4 in the upper wall of each furnace. Ash pits 5 and 8 are provided in the bottom walls of such furnace chambers.

In each of said furnaces is 'a tubular boiler of standard construction, consisting of top and bot tom drums connected by vertical tubes, which latter are directly exposed to the hot products of combustion. The first .boiler'comprises top and bottom drums I and 8, with tubes .9 extending therebetween, and the second boiler top and bottom drums l and H with tubes l2 therebetween. A third pair of top and bottom drums I3 and H with tubes l connecting them constitutes a waste heat boiler or economizer I8, located in the rear portion of the furnace chamber adjacent to the exit opening it. Connected with such exit I6 is a heat interchanging apparatus l1, through which the products of combustion from the fur nace pass to the stack. The cold air enters by way of duct l8 and is preheated in the heat inter changer ll, whence it is conveyed to combustio chamber I by a duct l9, in which is a fan 20.

The mechanism for supplying fuelto the nozzles 3 and 4 comprises a hopper 2| having branches 22 and 23 that lead to said nozzles, respectively,

combined with a rotatable spout 24 located above said hopper and arranged to receive the fuel from a continuous feed device 25, such as a screw con-. veyor. The conduit 26 leading from feed device 25 to rotating spout 24 is provided with a branch I 21 that leads back to the fuel storage bin, and

with a valve or gate 21a for controlling the feed to spout 24. A motor 28 serves to drive the fuel feed conveyor 25 and also to rotate the spout 24 in unison therewith. v v

The high boiling point fluid, diphenyloxide, which is to be vaporized in primary generator A, is received through a supply pipe 30 into the lower drum l4 of the waste heat boiler or economizer 18; A pipe 3| from the upper drum I 3 of economizer 18 leads to a pump 32, driven by motor 34, the discharge pipe 33 of which is branched, one

branch leading to drum 8 and the other to drum II. From the upper drums 1 and I 0 of the boil-- ers, the vapor is conducted by vapor duct 35 toa turbine 36, which is shown direct-connected to electrical generator 31, the current from the latter being led through wires 38 to bus bars 39.

The high boiling point vapor, after passing through turbine 36, and expanding therein so as to be partially cooled but still containing a considerable proportion of the original heat energy,

bus bars 39. The low boiling point vapor after passing through turbine 46 is received in a condenser 49 and from the latter the condensate is returned by means of pump 50 and return line 51 to the condenser boiler B. A valve-controlled supply line 52 is shown, by which the body of fluid in the secondary system may be replenished when necessary.

The condenser boiler B is designed to have less heat capacity in the low boiling point fluid than is imparted to it by the condensation of the high boiling point fluid in a given time; the condenser boiler being designed to have the lowest possible heat storage capacity commensurate with the operation of the system, thus allowing it to respond quickly to load variations and so facilitate governing the entire system. A much simpler system of control isaccordingly rendered possible than where the two vapor generators require to be separately controlled by separate governors. A safety valve 60 will be desirably provided in connection with the primary generator, e. g. on vapor line 35 as shown, but it would be set at so high a pressure that it will operate only under conditions of special emergency. A governor GI 01' any desired detailed construction on the turbine 46 that is operated by the low boiling point vapor will, where the load is very uniform, provide all the normal governing required. The action where abnormal governing is called for will be as fol1ows:-If the load goes off and governor 6| cuts down the vapor to turbine 46, the pressure and temperature will rapidly rise in the condenser boiler B and thereby graduallythrottle the primary turbine 36 by raising the exhaust pressure. too high so as to increase the pressure in condenser boiler B beyond a predetermined maximum, a safety valve 62 on said boiler is set to blow oif.

In addition to such safety valve 62, the con denser boiler 13 is provided with a pressure actuated device '63. This responds at a lower pressure than that forwhich said safety valve isset, to operate an adjustable electric contact 64 and thereby energize through a relay circuit 65, standard electrical control devices 66 and 66a associated, respectively, with the motor-driven fan 20 that supplies air to the combustion cham-. bers of the primary vapor generator A, and with motor 34. Similar standard electrical control devices 61 and 68 are respectively associated with the motor 28 whereby fuel supply device 25 is operated, and with gate 21a. It will accordingly be seen that as a result of an increase of the pressure within the condenser boiler B to the point where said device 63 is actuated, the rate of supply of air as well as the rate of feed of fuel to the primary heat source may be regulated or such respective supplies entirely shut oflf.

A vacuum pump 10 is connected with condenser boiler B by means of a pipe II. Thedischarge pipe 12 from the pump includes a condenser coil 13 and thence leads to a-storage tank 14 that is also provided with .an external valve controlled supply line 14a. From said storage or reserve tank 14 a pipe 15 leads into a return pipe 16 from the condenser boiler B, a pump 11 being connected with said return pipe beyond the point .of junction of pipe 15 therewith, and discharging into the pipe 30 to feed the high boiling point fluid to the waste heat boiler or economizer section of the primary vapor generator A.

Reference has hereinbefore been made to the advantageous use in above described binary fluid Should the temperature get.

power system of diphenyloxide and water as the two, fluids having properly disparate boiling points and other desirable characteristics. So far as known, diphenyloxide has never been successfully used for heat transfer purposes or in a system of the type in question. It is found, however, that as indicated by the charts comprising Figs. T and 3 that this substance has highly: desire! -e qualities for the purpose in hand, particularly when compared with mercury which has been proposed for use in an analogous manner. One principal objection to mercury aside from its first cost is the fact that it condenses on adiabatic expansion, whereas diphenyloxide superheats under the same circumstances. It is accordingly unusually well adapted for turbine work and having a vapor density over nine times as great as that of steam, a turbine may be operated therewith at a markedly lower velocity than steam to develop the same power. The cost of diphenyloxide, moreover, is less than two per cent of the cost of an equal volume of mercury, and it is found that, where properly prepared and purified, diphenyloxide may be subjected to prolonged boiling at pressures and temperatures suchas would be required for use in a power system of the type in hand, with almost no decomposition. The specific heat of diphenyloxide is 0.4 at moderate pressures and its critical pressure is 435 pounds per sq. in. absolute at 510 C., which is approximately 950 F.

While theoretically mercury would show greater efficiency were it possible to operate a generating plant at a very high temperature, the heat resistance of materials available for furnace construction imposes a definite limitation on the temperature that can be actually used under working conditions and at such maximum permissible temperatures, as shown by the temperature-entropy diagram (Fig. 3), diphenyloxide is approximately just as efficient as mercury.

As hereinbefore stated, the condenser boiler B is in effect a heat interchanger wherein heat is transferred from the condensing vapor of the high boiling point fluid, diphenyl oxide, to the water which is vaporized therein. Such use of diphenyl oxide as heat transfer agent is capable of much wider and more general application, and is not limited to a power system of the type just described. In fact, diphenyl oxide may be used to transfer heat to, or remove heat from, .liquid, gaseous or solid materials generally, and as a heat transfer medium it may be employed either as liquid or vapor. Many processes require the maintenance of relatively constant temperatures, such as in heat treating, fractional distillation, etc. Diphenyl oxide lends itself admirably for use as a heat transfer agent in such processes at temperatures as high as 750 F. for long periods of time without undergoing material decomposition, and in fact may be used at temperatures as high as 1000 F., i. e. above its critical temperature, with a relatively small amount of decomposition.

A heating temperature of 500 F. may be attained with the use of diphenyl oxide vapor at slightly more than atmospheric pressure, whereas with water vapor a temperature of about 212 F. is the highest obtainable at such pressure. At a pressure of 100 pounds per square inch absolute, a heating temperature of 100 F. may be attained with diphenyl oxide, whereas with water vapor at that pressure the highest attainable temperature would be about 327 F. To obtain a temperature of 700 F. with water vapor the pressure would have to be raised to approximately 3000 pounds per square inch. Clearly, diphenyl oxide affords marked advantages for use as heat transfer agent, especially in the temperature range of 500 to 750 F., since it is stable at these temperatures and may be heated thereto repeatedly and maintained at such temperatures for long periods of time without undergoing material decomposition or modification of physical properties.

Other modes of applying the principle of the invention may be employed instead of those explained, change being made as regards the means and the steps herein disclosed, provided those stated by any of the following claims or their equivalent be employed.

It is, therefore, particularly pointed out and distinctly claimed as the invention:

2,ooo,ese

3 1. The method of transferring heat which comprises heating a body of diphenyloxide to a temperature between-500 and 750 F. and passingthe same in indirect heat transfer relation with a body of a material to be heated.

2. The method of transferring heat which comprises vaporizing a body of diphenyloxide at a temperature between 500 and 750 F., conducting the vapors to a zone of heat exchange and condensing the vapors therein by passing in indirect thermal contact with a body of heat-receiving material.

WILLARD I-I. DOW,

CLARA TURNER.

Admimstrators of the Estate of Herbert H. D010. 15

Deceased. 

